Sheave



D. FIRTH 2,413,817

Jan. 7,1947.

SHEAVE Filed Feb. '5, 1945 I I INVENTOR. lYQZJLZJZrZ /W,

Patented Jan. 7, 1947 SHEAVE David Firth, South Bend, Ind., assignor toDodge Manufacturing Corporation, Mishawaka, Ind., a corporation ofIndiana Application February 5, 1943, Serial No. 474,830

Claims.

Sheaves for multiple V-belt drives should have accurately formedbelt'grooves the side walls of which should be uniformly wear-resistant.Wear resulting in. material enlargement of the belt grooves isobjectionable as altering established pitch diameters. Unequal wear ofthe belt grooves would be especially objectionable as interfering withthe important objective of maintaining the rubber driving belts equallytensioned and therefore in engagement with the sheaves at uniformdistances from the sheave axes.

For conservation of metal, it is desirable to utilize wood or othersuitable non-metallic material for the construction. of such sheaves.Wood sheaves of suitable construction can be used uncler many conditionsfor duties for whichcast iron sheaves of corresponding sizes have beencommonly employed. The wood sheaves are of relatively light weight,which is importantly advantageous in transportation. Furthermore, thewood sheaves can be driven at faster speeds than the cast iron sheaveswithout going to pieces by centrifugal force. However, the wearingqualities of wood sheaves are generally interior to those of cast iron.

Sheaves having tractive surfaces of hard wood transverse of the grainthereof are satisfactorily wear-resistant under ordinary conditions; however the fabrication of wood sheaves so as to dispose the grain of thewood transversely of the tractive surfaces for substantially or nearlythe entire circumference necessitates special shaping and arrangement ofwood pieces, increasin labor and cost of production. Unless sofabricated, a wood sheave is liable to wear unevenly, due to presence ofsoft spots or inequalities of hardness in its tractive surfaces.Moreover a wood sheave is liable to wear down rapidly it operated in thepresence of abrasive dust or used under conditions such as to beaffected by grit between the driving belts and walls of the sheavegrooves.

It is therefore desirable to provide a wood sheave with groove wallshaving hard metal wear surfaces. The present invention provides such asheave of practicable character, readily and economically producible indesired forms and sizes.

A sheave embodying the invention ,is characterized by a sheave body ofwood or other suitable non-metallic material having a metallic skinlikecoating formed on, covering and bonded to the perimeter thereof andproviding circumferentially continuous groove wall liners, the exteriorof the coating or belt-engaging portions thereof being ground ormachined and ground to provide smooth tractive surfaces. Thus theinvention gives the advantage of a relatively light construction ofnon-metallic material with the wearing qualities of a metallic sheave.Further advantages of the invention will be hereinafter 7 indicated.

In the accompanying drawing, there is shown for illustration a, multipleV-belt sheave of one practicable construction embodying the invention.

Fig. 1 is a section of the illustrative sheave taken on a planelongitudinally of and through the sheave axis.

Fig. 2 shows a fragment of the rim portion of the sheave partly insection and partly in end elevation, this view being a portion of thatshown on a reduced scale in Fig. 3.

Fig. 3 on a reduced. scale shows the sheave half in cross section on theline 3-3 of Fig. 1 and half in end elevation.

Fig. 4 is a diagrammatic representation in section of an enlargedfragment of the rim portion of the sheave.

In the drawing, I designates as a whole a laminatecl wood sheave bodythe perimeter of which is formed to provide annular'belt grooves 2 ofV-shaped cross section. Formed on and covering the perimeter and liningthe walls of the belt grooves is a hard skin-like coating 3 of ferrousmetal or other suitable metallic material, the coating being bonded tothe wood material of the body perimeter by engagement of numerous minuteportions of the metallic coating in pores or interstices of the wood.The coating conforms in exterior shape substantially to the contour ofthe body perimeter, and, as best shown in Fig. 4, the portions of thecoating lining the side walls of the belt grooves are ground to providesmooth surfaces for engagement by the V-belts, these being conicalsurfaces concentric with and of the same slant as the correspondingsurfaces providing the side walls of the body grooves.

The coating may be formed by spraying atomized or finely divided moltenof semi-molten particles of metal on the perimeter of the wood sheavebody and on the film of such particles so deposited until there is builtup a coating of desired thickness. This involves utilization of a methodwhich is in industrial use for the coating of metal surfaces to providecorrosion-resistant and wear-resistant coatings and which has also beenapplied to the coating of glass, paper and wood for ornamentation. Themethod is carried out with the use of known apparatus including a spraygun through the nozzle of which is fed at a constant rate a wire'composed of the metal to supply the coating material. Concentricchambers of the spray gun are connected respectively with sources ofoXy-acetylene gas, oXy-hydrogen gas and compressed air. At the nozzle ofthe spray gun the wire is melted by an oXy-acetylone or oXy-hydrogenflame and as it melts is subiected to a blast of compressed air, wherebythe molten or melting metal is atomized and sprayed off. As the finelydivided molten or semi-molten metal particles strike the wood surface ofthe sheave body perimeter, they rapidly chill and solidify, becomingbonded to said perimeter by keying in surface pores or interstices ofthe wood, and bonding and integrating with successively depositedparticles. There is thus formed a coating of substantially uniform orhomogeneous nature, composed of integrated and interbonded metallicgrains, which can be easily machined and ground. The coating issusceptible of taking a very smooth and even glossy finish by polishing.A ground and polished surface of a coating of ferrous metal so formedhas something of the aspect of polished granite.

The coating 3 may be of ferrous or other desired metal or alloy ormetallic material com posed mainly of metal but containing carbon,silicon or other elements. For example the coating may be of metal of acast iron or hard steel composition or of alloy steel.

lhe coating may be of say about the thickness of heavy paper or thincardboard or of greater thickness if desired. Usually a coating of notmore than about one sixty-fourth of an inch thick is preferable to oneof greater thickness, it being desirable to conserve the use of coatingmetal as Well as to avoid undue increase of weight of the wood sheave.

The coating provides not only smooth hard tractive surfaces for the beltgroove walls but also a protective armor for the perimeter of the woodsheave body, preventing scuffing or chipping thereof or breakage of thenarrow wood ribs formed between the belt grooves, and reinforces andstrengthens the wood sheave body.

Thus the invention substantially increases the practicability andefi'iciency of a wood sheave; obtains the advantage of a relativelylight construction of non-metallic material with the durability andwearing qualities of a cast iron or hard metal sheave; renders itunnecessary to fabricate wood sheaves with the grain of the woodpresented transversely of'the tractive surfaces for substantially ornearly the entire circumference; and provides a construction whichpermits the use of soft wood, paper board or other relatively soft,light, cheap materials for the sheave body.

It is contemplated that the bodies of sheaves embodying the inventionmay be made variously from non-metallic materials of the classcomprising wood, paper and the like, including plywood, paper board,papienmach, fibre board and analogous materials, and also such moldableplastics .as may be suitable for sheave bodies and susceptible ofcoating of their perimeters by the method described without injuriouseffect upon the peripheral contours of the molded bodies.

The invention is thus conducive to promoting the utilization of wood andother non-metallic materials for sheave construction. In this connectionan important advantage of the invention is that manufacture thereof isnot limited to particular forms and sizes by the use of dies, molds andthe like; the wood or non-metallic bodies being readily producible indesired forms and sizes, to meet dii ferent requirements as to pitchdiameters and members of belt grooves, and the 4 metallic coatings beingeasily applicable to any forms and sizes thereof.

Another advantage of the invention is that the metallic coating 3 may beelectrically connected with the sheave shaft, for conducting ofi staticelectricity accumulating on the rubber driving belts running'in tractiveengagement with the sheave, thereby affording protection from sparkingby static electrical discharges, which is of great importance forinstallations where electric sparks would be liable to cause explosions;thus further increasing the practicability of wood sheaves or enlargingthe field in which they can be utilized. Electrical connection of thecoatin 3 with the sheave shaft may be made simply and inexpensively by astrip of metallic coating material 4 formed on the face of the woodsheave body and leading from the coating 3 to the shaft. In the case ofthe illustrative sheave, which is of the split contractible hub type andhas fitted in its hub bore a split contractible wood bushing 5. theconducting strip i is continued across the end of the bushing asindicated at 6 in Fig. 3, or, more accurately speaking, the conductingstrip 4 contacts with conducting material formed on the bushing at 6 andcontacting with the shaft.

With respect to its body construction and mode of mounting, theillustrative sheave is in accord ance with and embodies the inventiondisclosed in the pending patent application of Firth and Lower, SerialNo. 458,829, filed August 6, 1942, now Patent No. 2,352,474, dated June27, 1944. The sheave body, comprising hub and rim portions and aconnecting Web portion, is built up of adhesively joined wood plies orlaminations arranged transversely of the sheave axis. The weblaminations and corresponding laminations of the hub and rim portions ofthe sheave body are provided by the intermediate discs 1' and outerdiscs 8. Additional laminations of the rim portion of the sheave body,forming overhanging extension thereof, are provided by the rim rings 9and facing rings Eli. Additional hub laminations are provided by thecomplemental halves ll of hub discs divided by the radial slots 12.

The several discs, rings and half discs referred to may be one pieceelements or some or all of them may be composed of suitable jointedsmaller wood pieces.

Cut through the laminated wood sheave body, at opposite sides of andspaced from the sheave bore, are a pair of large openings 13 the innerflat walls Hi of which are parallel-and perpendicular to the diametricplane A--B bisecting said openings. The portion of the sheave bodybetween the openings is divided longitudinally of the axis by the slots[2 extending radially from the hub bore .to diametrically oppositepoints beyond the circumference of the hub. The slots 52, as Well as theopenings I3, extend clear through the sheave body as shown in Fig. 1.There is thus provided a contractible split hub unitary with thesurrounding rim portion of the sheave body.

The parts of the hub at opposite sides of the slots 12 are connected bybolts consisting preferably of slender metal rods it having screwthreaded end portions engaged by the nuts I6 accommodated in theopenings 53, flat metal washers ill being interposed between the boltnuts and flat walls l4- forming the opposite sides of the sheave hub. Bytightening said nuts, the sheave hub can be contracted on thecontractile bushing 5 to clamp the sheave to the bushing and the latterto the shaft, whereby to secure the sheave in fixed relation to anddriving connection with the shaft.

The bushing 5, which may be of metal but is preferably of wood, is splitlongitudinally by a slot l8 extending the full length of the bushing. Inits uncontracted state the bushing fits the hub bore of the sheave andthe shaft to which it is applied, though in view of the contractibilityof the bushing the shaft may be of slightly less diameter than the boreof the bushing. The sheave can be used with wood bushings of differentinside diameters to adapt it to shafts of different diameters.

One practicable method of making a sheave body of the constructiondescribed (which can be made in several different ways) is as follows.First there is built up or fabricated in the rough a laminated wood bodyor pile of adhesively joined wood discs, either integral or composite,to provide the laminations for the hub and web and intermediate portionof the rim or all except the overhanging extensions of the rim portionof the sheave body. Having built up such laminated wood body in anyappropriate manner, the next step is to bore a center hole therethroughto provide the hub bore. Next the openings I3 are cut through said body.Then said body is split by sawing through it on the diametric line C-D,using a thick saw through the part of the body which is to form the huband web, so as to provide the radial slots l2, and using a thin sawthrough the surrounding or outer portion of the laminated body. Saidbody is thus divided into two identical half parts. Now the holes forthe hub bolts are drilled in said half parts, and the 2 bolt rods I5 areinserted in said half parts which are then glued back together again;or, after inserting said bolt rods the said two half parts may be joinedby suitably keying them together. After these operations there are addedwood rings to provide the laminations for the rim extensions of thesheave body, such added wood rings being adhesively united to said bodyand to one another. The unfinished sheave body thus made in the rough isnow put into a lathe and shaped to the form desired, as, for example,that shown in Fig. l.

It will be apparent that in the case of a sheave body of theconstruction described, the

metallic coating 3, forming a continuous binding around its perimeter,ties together the several laminations of the rim portion of the body andeffectually reinforces and strengthens the structure.

The particular construction of sheave shown and described will beunderstood to be exemplary, the invention being applicable tonon-metallic sheaves of various different forms and constructions andadapted to be mounted by various different means on the sheave shafts oron sleeves to be applied to the shafts.

In making a sheave embodying the invention, the wood sheave body ismounted in a suitable machine in which it is rotated about its axis, andthe metallic coating material is sprayed on its perimeter while it is sorotated, whereby to obtain a coating of substantially uniform thickness.

I claim:

1. A sheave for power transmission comprising a peripherally groovedsheave body of wood or other suitable non-metallic material having athin coating of metal covering and adhering di rectly to its perimeterand lining the groovetyalls thereof, said coating being composed ofintegrated separately formed grains and bonded to said walls in drivingconnection therewith by engagement of such grains in surface pores orinter,-

stices of said non-metallic material, and the por tions of said coatinglining said groove walls;

having ground smooth belt-engaging surfaces.

2. A sheave for power transmission comprising a sheave body of wood orother suitable nonmetallic material having a plurality of annular beltgrooves formed in its perimeter and a circumferentially continuous andseamless thin metallic sheathing conforming to the contour of andcovering said perimeter and lining the walls of said grooves, saidsheathing being a metallic coating fitting as a skin and adheringdirectly to said perimeter in driving connection therewith and theportions thereof lining the walls of said grooves having ground smoothbelt-engaging surfaces.

3. A sheave for power transmission comprising a sheave body of wood orother suitable non-metallic material of laminated formation with itsplies or laminations arranged transversely of the sheave axis and havinga plurality of annular belt grooves formed in its perimeter, and acircumferentially continuous and seamless thin metallic sheathingconforming to the contour of and covering said perimeter and lining thewalls of said grooves, said sheathing being a metallic coating fittingas a skin and adhering directly to and binding said perimeter in drivingconnection therewith and tying together the plies or laminations of therim portion of the sheave, and the portions of said coating lining saidgroove walls having ground smooth belt-engaging surfaces.

4. A V-belt sheave for power transmission comprising a sheave body ofwood or other suitable non-metallic material having one or more annularbelt-grooves of V-shaped cross section formed in its perimeter andhaving circumferentially continuous thin metallic films lining the wallsof said grooves and adhering directly thereto in driving connectiontherewith, said films having smooth belt-engaging surfaces.

5. A V-belt sheave for power transmission comprising a sheave body ofwood or other suitable non-metallic material having a plurality ofannular belt grooves of V-shaped cross-section formed in its perimeterand a circumferentially continuous and seamless thin metallic sheathingconforming to the contour of and covering said perimeter and lining thewalls of said grooves, said sheathing being a metallic coating fittingas a skin and adhering directly to said perimeter in driving connectiontherewith, the coating being composed of integrated separately formedgrains and bonded to said walls by engagement of such grains in surfacepores or interstices of said nonmetallic material, and the portions ofsaid coating lining said groove walls having ground smooth belt-engagingsurfaces.

DAVID FIRTH.

